libgo: update to go1.15rc1

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/245157

2 files changed, 14 insertions, 1 deletions

diff --git a/libgo/go/errors/wrap.go b/libgo/go/errors/wrap.go
index 272d056b318..b82ca34b46f 100644
--- a/libgo/go/errors/wrap.go
+++ b/libgo/go/errors/wrap.go
@@ -70,7 +70,7 @@ func Is(err, target error) bool {
 // setting target.
 //
 // An error type might provide an As method so it can be treated as if it were a
-// a different error type.
+// different error type.
 //
 // As panics if target is not a non-nil pointer to either a type that implements
 // error, or to any interface type.
diff --git a/libgo/go/errors/wrap_test.go b/libgo/go/errors/wrap_test.go
index 590c1857e37..4a4a732c9be 100644
--- a/libgo/go/errors/wrap_test.go
+++ b/libgo/go/errors/wrap_test.go
@@ -238,6 +238,19 @@ func (errorUncomparable) Is(target error) bool {
 	return ok
 }
 
+func ExampleIs() {
+	if _, err := os.Open("non-existing"); err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			fmt.Println("file does not exist")
+		} else {
+			fmt.Println(err)
+		}
+	}
+
+	// Output:
+	// file does not exist
+}
+
 func ExampleAs() {
 	if _, err := os.Open("non-existing"); err != nil {
 		var pathError *os.PathError